1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device including a test pixel for detecting light leakage and a method of fabricating a black matrix using the test pixel.
2. Description of the Background Art
As visual display devices become increasingly important as visual information transmitting media, the display devices must have low power consumption, high image quality, light weight, and a thin profile. Currently, liquid crystal display (LCD) devices are employed in flat panel displays (FPDs) due to their simplicity of fabrication, and are rapidly replacing cathode ray tube (CRT) devices.
The LCD devices include a first substrate to function as an array substrate, a second substrate to function as a color filter substrate, and a liquid crystal layer formed between the first and second substrates. Pixel electrodes and a common electrode are formed as transparent conducting layers on the array substrate and the color filter substrate, respectively, in order to induce an electric field to the liquid crystal layer. In addition, aligning layers are formed on the pairs of pixel and common electrodes.
Liquid crystal molecules of the liquid crystal layer are initially aligned along a specific direction using the aligning layers and a rubbing process. Within specific regions, the liquid crystal molecules are either uniformly aligned or are varied continuously. In order to provide an optimum display state, an entire liquid crystal cell must be disposed within a single region.
A boundary between two adjacent regions in which alignment of the liquid crystal molecules are varied discontinuously is commonly called a regional barrier. At the regional barrier, disclination phenomenon occurs in which the alignment of the liquid crystal molecules is varied discontinuously. In particular, in a liquid crystal display device having many of conductive lines (i.e., gate lines, data lines, storage capacity electrode lines, etc.) formed, horizontal and vertical electric fields are generated between the conductive lines. Thus, the horizontal electric field is a main contributing factor for generating the disclination phenomenon. As a result of the disclination phenomenon, light may leak from edges of the pixel electrode, thereby lowering contrast ratios due to the light leakage.
FIG. 1 is a plan view of a liquid crystal display device demonstrating the light leakage phenomenon according to the related art. In FIG. 1, a portion within a pixel 110 marked with oblique lines indicates a light leakage region. Accordingly, since it is impossible to adjust alignment of liquid crystal molecules within a disclination phenomenon occurring region, the region has to be covered with a black matrix 100. In addition, if the black matrix 100 is not precisely designed, the light leakage portion inevitably occurs within a region where the black matrix 100 does not exist. Accordingly, the disclination phenomenon acts as a very important factor in determining intervals between adjacent conductive lines of the liquid crystal display device and designing of the black matrix 100.
In order to determine optimum intervals between the conductive lines and an optimum width of the black matrix, consideration of a bonding margin of the array substrate and the color filter substrate, misalignment of the black matrix, and stepped regions of thin film transistors (TFTs) must be given. In addition, under a microscope having high magnification, the disclination phenomenon can be calculated. Then, by applying the result to a mask, the light phenomenon can be resolved by designing the liquid crystal display panel through repeated trial and error processes. However, the liquid crystal display device has to be disassembled and observed in order to get an accurate result. Moreover, it is still impossible to obtain accurate information about the disclination phenomenon.